ETA relevant links: https://youtube.com/@NotJustBikes https://letgrow.org/
ETA again: I glibly mentioned "being killed by a driver" but of course navigating the typical US built environment if you're under 16 or otherwise unable to drive is a miserable experience in a number of ways even if you survive it. Highways make pedestrian paths unnecessarily roundabout. Parking lots make everything further from everything else. Crossing major roads requires getting drivers to notice and stop for you (harder when you're short!), or waiting through interminable signal cycles, etc.
It may depends on where in the US you're talking about, but in my area none of this is actually true. Although lots of people believe it is.
I do worry about car on pedestrian crashes but the city has crossing guards and traffic calming for just this.
Where are these places that you can’t be outside as a child?
[1] https://www.google.co.nz/maps/@33.8644514,-84.5949946,3a,75y...
[2] https://www.google.co.nz/maps/@-41.2953813,174.7673872,3a,75...
edit: Might add that close to those shops in [2] there is a large botanic garden with play area and stream, one small and one very large reserve with native bush and an abundance of mountain bike tracks, a playing field, the central city area with cafes, many theatres, galleries, a library, and all sorts of other things that a child can make use of without supervision. All of this is within 5 minutes walk of those shops. Within 10 minutes walk there is the waterfront and a very safe swimming beach.
I mean drive around a little in the place you picked - do you see any houses? Now move your map a couple miles in any direction and you'll see forests with walking trails, ponds, parks, small streets where kids can play on the street. That's what it's actually like.
When I explore that area surrounding the commercial zone in Atlanta I find just houses, green spaces, and roads. It's a crappy environment for anyone without a car (e.g. kids).
People in the US don't like that, they like central large stores in one area, and then residences without any business nearby. You are wrong though, it's actually very nice for the kids, they can play without worry. But they can't go shopping. Big deal, that hardly matters.
I lived in a place like that, it's actually a really nice way to grow up. Much better than the packed-in way that they do it in Europe or New York. Instead of stores, you have space. And yes, you can play in the road, there's not that many cars, since the only driving nearby is if you live there. And kids can and do, ride bikes all over the place, because again, hardly any cars.
It's different tradeoffs. Also don't forget America is big, really really big. Without a car you basically can't go anywhere, America is too big for public transport to work, with the exception of a couple large cities.
And they like it that way.
Americans don't want to live closely packed near other people. They like having space. The like having huge houses, and huge yards. They like not hearing the neighbors. (And if you want something different, you can live in a large city.)
I've been in the kinds of cities you seem to like, and I find them miserable experiences, it's so crowded, you can't get away from people! The stores are so small, the selection is terrible and the costs high. And you can't go anywhere since you need a bus to do anything (which means you can't take very much with you, and you don't have anyplace to store things), instead of just hop in your car. You can go anywhere, you can leave your possessions locked in your car, so you don't have to carry them.
I've talked to people who used to live in New York, then moved out, and they act like prisoners who found freedom. They had no idea how nice it is to live somewhere with space. Yes you need a car for that, but that's hardly a problem.